1. Field of the Invention
The present invention relates to a printing apparatus and an image forming apparatus.
2. Description of the Related Art
Conventional network printers sequentially receive and store a plurality of print jobs, and process the print jobs in the order in which they are received. By assigning a priority to a print job, the print job can be preferentially printed. Besides, a print job can also be paused or restarted. When any print job is specified to be paused, the print job is suspended, and a subsequent print job is printed before the print job. When the restart of printing is specified, the order of print jobs is rearranged according to a predetermined method that varies depending on the type of printer, and the print jobs are printed in the order.
Japanese Patent Application Laid-Open No. 2002-157098 discloses print-job management device which increases a variation of states upon management of print jobs to improve printer usability. In a printing system structured via a network, a job management device is provided in a printer to manage states of the print jobs according to international standards. In this case, a create control unit is provided in addition to function blocks for processing the print jobs according to the standards. When a user sends an “create” instruction for the print job of which execution is held, the create control unit newly generates a slave job using the print job instructed as a master job, and executes printing of either one of the jobs. At least one of the print jobs is kept in its held state and stored as it is, and a document stored can thereby be repeatedly printed at any time.
Japanese Patent Application Laid-Open No. 2003-131828 discloses image forming apparatus which controls a process order of a plurality of print jobs which are requested from a plurality of uses. A job control unit acquires job attribute information in a print queue. When the state is a “wait for completion of preceding job” state, the job control unit determines that the print job is not a target for print order control, and acquires job attribute information for a next print job. When the state is not the “wait for completion of preceding job” state, the job control unit determines whether the start of execution is held. If the state is changed to the “wait for completion of preceding job” state or to a “Sprint wait” state, the job control unit acquires job attribute information for a next print job. Furthermore, when the print job subjected to the process of “determination whether to hold the start of execution” is changed to “printing”, the job control unit determines that the start of printing process is possible and starts execution. The job control unit repeats the print order control until any print job which is not in the “wait for completion of preceding job” state or in the “print wait” state is detected.
Japanese Patent Application Laid-Open No. 2003-305928 discloses image forming apparatus which holds a job, with which an error occurs, in the apparatus and can specify restart of the job whenever a user wants it. The image forming apparatus can process a plurality of continuous jobs. The image forming apparatus includes an operation panel, a storage unit, a set-contents management unit that manages various set contents, and a data processing unit. When the printing process is suspended due to an error during printing, the print data from a relevant page to the last page of the job being paused is stored in the storage unit as a print-uncompleted document by entry of an instruction through the operation panel, and the printing process of the relevant job is terminated. By entry of a restart instruction of the document stored in the storage unit, printing of the job interrupted due to the error is restarted from the page where the error has occurred.
In the conventional printers, however, to restart a print job being paused, the execution order of the print job is not considered at all. Therefore, the user does not know when the print job is printed. In another case, the execution order of the print job to be restarted is fixed and cannot be changed.
In recent years, networking of personal computers (PCs) is progressed, and a network-type image forming system is structured in such a manner that an image forming apparatus such as a printer is connected to not only one PC but a plurality of PCs via a network to enable sharing of the printer with the PCs.
The image forming apparatus used in the network-type image forming system incorporates a spooler function, and hence, it is configured to accept a subsequent print job before completion of a preceding print job.
The spooler has a function of temporarily storing print data of a plurality of print jobs received via the network in the image forming apparatus, and a function of managing the printing order of the print jobs. When a subsequent print job is received before the preceding print job is not completed, the subsequent print job is changed to the “print wait” state in the spooler.
Each print job can be provided with an attribute of preferential printing. When the print jobs in which a higher-priority print job and an ordinary print job are mixed are in the print wait state, the higher-priority print job can also be preferentially printed. Moreover, some of the printers have a function of estimating a printing time.
Japanese Patent Application Laid-Open No. 2005-324471 discloses an image forming apparatus capable of preferentially printing a higher-priority print job and accepting a subsequent print job before completion of a preceding print job. The image forming apparatus includes a setting unit that sets a maximum printing time for each user or each print job; an estimating unit that estimates the time when the print job is received, the time when the process is started, or the amount of time required from start of printing to completion of the printing; and a control unit that controls so as to delay the start of printing of the print job when the time required is shorter than the maximum printing time of the print job. This allows the image forming apparatus to preferentially print the higher-priority print job or to print another print job in parallel or preferentially. In the image forming apparatus, however, if “memory full” occurs in the image forming apparatus when print data of a plurality of print jobs are temporarily stored therein, this causes occurrence of such a state that a subsequent printing process or the like cannot be performed.
The printing process has been performed by image forming apparatuses. Recently, in particular, an increase in printing speed has been demanded of the image forming apparatuses.
For example, Japanese Patent Application Laid-Open No. H11-098332 discloses an image forming apparatus capable of continuing facsimile reception without disconnecting a line even if the printer is in the copying operation when the memory full occurs during facsimile reception.
Japanese Patent Application Laid-Open No. 2004-235769 discloses an image forming apparatus that causes another image forming apparatus connected to a network to form an image when the image forming apparatus has run out of memory.
In the conventional examples, however, to preferentially print an urgent job, the image forming apparatuses can pause a job to cause a subsequent job to be processed before the process of the job, but if the image forming apparatus has run out of storage space due to jobs being paused, a next process cannot be performed.
As for conventional printers for printing print data received, there is known a technology of executing print jobs in the order in which the print data is received. In the technology, once reception of one print data is started, the printer cannot receive another print data until the reception is completed. If a large amount of print data is received or if a print job is paused due to shortage of paper or so, a print job subsequently instructed cannot be printed until a print job previously instructed is completed.
As a printer configured to solve the problems, Japanese Patent Application Laid-Open No. 2002-36675 discloses a printer as follows. When a print job is instructed so as to be printed preferentially to the printing process of a print job currently performed, the printer stores print pages created from print data being currently received, and completes the printing process of the print job to be preferentially output, and then prints the print pages stored. In the conventional technology, however, if the print job of which printing has been started is once paused, some printed results are output by the time the print job is paused, and thereafter, a preferentially printed result is output. Therefore, the printed results for one print job cannot continuously be output. This may sometimes lead to a case where the printed result of the user gets mixed with other printed results.
Moreover, because the pause can be instructed for all the print jobs which are in the print wait in a certain printer, if a user is about to pause the printing process, the user may erroneously pause a print job of another user, or another user may erroneously indicate “print restart” or “print pause”. These sorts of failures may sometimes happen.
Furthermore, because the operation for printing is required for each print job, if a plurality of print requests are made, instructions to pause the printing and instructions to restart the printing of the print jobs are complicated, which imposes heavy workloads on users.